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OAC-ALONE, the first randomized trial to test the efficacy of oral anticoagulation (OAC) alone against combined OAC and a single antiplatelet agent (APT) in patients with atrial fibrillation (AFib) and stable coronary artery disease, was unable to establish noninferiority of OACs to dual therapy, according to data presented at the 30th annual TCT conference in San Diego.

Yukiko Nakano, MD, of the Kyoto University Graduate School of Medicine in Kyoto, Japan, headed the study, which launched in 2013.

“In patients with concomitant [AFib] and stable coronary artery disease beyond one year after coronary stent implantation, the ESC guidelines have consistently recommended oral anticoagulation without antiplatelet therapy,” Nakano told the press. “In clinical practice, however, antiplatelet therapy is often used on top of OAC beyond one year after coronary stenting. Importantly, no randomized controlled trials have evaluated OAC monotherapy in this patient subset.”

Nakano’s study was built to enroll 2,000 patients over a 12-month period, but enrollment was cut short in December 2016 after the team had only managed to recruit 696 patients over a three-year span. The trial forged ahead with its smaller sample size, half of whom were randomized to OAC therapy alone and the other half of whom were randomized to combined OAC and APT. OACs were warfarin 75 percent of the time and direct OACs the other 25 percent.

Just less than 16 percent of patients in the OAC-only group and 13.6 percent of those in the combined therapy group met the primary endpoint of the study, which was a composite of all-cause death, myocardial infarction, stroke or systemic embolism. Another 67 patients in each cohort met the study’s secondary endpoint of major bleeding.

Eight patients taking only OACs experienced MI over the course of two and a half years of follow-up, Nakano reported, compared to four patients taking OACs and APT. Stroke or systemic embolism occurred in 13 and 19 patients, respectively, and major bleeding was a problem in 27 and 36 patients, respectively.

“Because the patient enrollment was prematurely terminated, the study was underpowered and inconclusive,” she said. “Larger, adequately powered randomized trials are required to establish the optimal antithrombotic regimen in this population.”